<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>

<div id="app">
  <h2 v-if="score>=90">优秀</h2>
  <h2 v-else-if="score>=80">良好</h2>
  <h2 v-else-if="score>=60">及格</h2>
  <h2 v-else>不及格</h2>

  <h1>{{result}}</h1>
</div>

<script src="../js/vue.js"></script>
<script>
  const app = new Vue({
    el: '#app',
    data: {
      score: 99
    },
    computed: {
      result() {
        let showMessage = '';
        if (this.score >= 90) {
          showMessage = '优秀'
        } else if (this.score >= 80) {
          showMessage = '良好'
        }
        // ...
        return showMessage
      }
    }
  })
</script>

</body>
</html>